Method and apparatus for data transmission of device-to-device user equipment in wireless communication system

ABSTRACT

According to an embodiment of the present invention, a method for transmitting Device-to-Device (D2D) data by a User Equipment (UE) in a wireless communication system, the method comprising: determining a bitmap to be applied to a subframe pool for data transmission from a subframe indicator bitmap; determining a set of subframes to transmit D2D data by using the bitmap to the subframe pool for data transmission; and transmitting D2D data in a subframe included in the determined subframe set, wherein a set of values available as k being the number of 1s in the subframe indicator bitmap are changed according to a Uplink/Downlink (UL/DL) configuration set to which a UL/DL configuration configured for the UE belongs.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. §119(e), this application claims the benefit ofU.S. Provisional Patent Application No(s). 62/042,228, filed on Aug. 26,2014 and 62/042,768, filed on Aug. 27, 2014, the contents of which areall hereby incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method and apparatus for transmitting data inDevice-to-Device (D2D) communication.

BACKGROUND ART

Wireless communication systems have been widely deployed to providevarious types of communication services such as voice or data. Ingeneral, a wireless communication system is a multiple access systemthat supports communication of multiple users by sharing availablesystem resources (a bandwidth, transmission power, etc.) among them. Forexample, multiple access systems include a Code Division Multiple Access(CDMA) system, a Frequency Division Multiple Access (FDMA) system, aTime Division Multiple Access (TDMA) system, an Orthogonal FrequencyDivision Multiple Access (OFDMA) system, a Single Carrier FrequencyDivision Multiple Access (SC-FDMA) system, and a Multi-Carrier FrequencyDivision Multiple Access (MC-FDMA) system.

D2D communication is a communication scheme in which a direct link isestablished between User Equipments (UEs) and the UEs exchange voice anddata directly with each other without intervention of an evolved Node B(eNB). D2D communication may cover UE-to-UE communication andpeer-to-peer communication. In addition, D2D communication may find itsapplications in Machine-to-Machine (M2M) communication and Machine TypeCommunication (MTC).

D2D communication is under consideration as a solution to the overheadof an eNB caused by rapidly increasing data traffic. For example, sincedevices exchange data directly with each other without intervention ofan eNB by D2D communication, compared to legacy wireless communication,the overhead of a network may be reduced. Further, it is expected thatwith the introduction of D2D communication will reduce the powerconsumption of devices participating in D2D communication, increase datatransmission rates, increase the accommodation capability of a network,distribute load, and extend cell coverage.

DISCLOSURE Technical Problem

An object of the present invention is to define a set of valuesavailable as the number of 1s included in a subframe indicator bitmap.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

Technical Solution

A first technical aspect of the present invention is a method fortransmitting Device-to-Device (D2D) data by a User Equipment (UE) in awireless communication system, the method comprising: determining abitmap to be applied to a subframe pool for data transmission from asubframe indicator bitmap; determining a set of subframes to transmitD2D data by using the bitmap to the subframe pool for data transmission;and transmitting D2D data in a subframe included in the determinedsubframe set, wherein a set of values available as k being the number of1s in the subframe indicator bitmap are changed according to aUplink/Downlink (UL/DL) configuration set to which a UL/DL configurationconfigured for the UE belongs.

A second technical aspect of the present invention is an apparatus of aUser Equipment (UE) for transmitting a Device-to-Device (D2D) signal ina wireless communication system, the apparatus comprising: atransmission module; and a processor, wherein the processor isconfigured to determine a bitmap to be applied to a subframe pool fordata transmission from a subframe indicator bitmap, to determine a setof subframes to transmit D2D data by using the bitmap to the subframepool for data transmission, and to transmit D2D data in a subframeincluded in the determined subframe set, and wherein a set of valuesavailable as k being the number of 1s in the subframe indicator bitmapare changed according to a Uplink/Downlink (UL/DL) configuration set towhich a UL/DL configuration configured for the UE belongs.

The UL/DL configuration configured for the UE is one of UL/DLconfigurations 1, 2, 4 and 5, the set of values available as k is {1, 2,4, 8}.

The UL/DL configuration configured for the UE is UL/DL configuration 0,the set of values available as k is {1, 2, 3, 4, 5, 6, 7}.

If the UL/DL configuration configured for the UE is one of UL/DLconfigurations 3 and 6, the set of values available as k is {1, 2, 3, 4,5, 6}.

The D2D data transmission is for transmission mode 1.

If the set of values available as k is {1, 2, 4, 8}, {1, 2, 3, 4, 5, 6,7}, or {1, 2, 3, 4, 5, 6}, the size of the subframe indicator bitmap is8, 7, or 6, respectively.

Advantageous Effects

According to at least one embodiment of present invention, delay whenusing time resource pattern and half duplex problem are solved.

The effects of the present invention are not limited to theabove-described effects and other effects which are not described hereinwill become apparent to those skilled in the art from the followingdescription.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates a radio frame structure;

FIG. 2 illustrates a structure of a downlink resource grid for theduration of one downlink slot;

FIG. 3 illustrates a structure of a downlink subframe;

FIG. 4 illustrates a structure of an uplink subframe;

FIG. 5 illustrates relay of a synchronization signal;

FIG. 6 illustrates a time resource pattern according to an embodiment ofthe present invention; and

FIG. 7 is a block diagram of a transmission apparatus and a receptionapparatus.

BEST MODE

The embodiments described below are constructed by combining elementsand features of the present invention in a predetermined form. Theelements or features may be considered selective unless explicitlymentioned otherwise. Each of the elements or features can be implementedwithout being combined with other elements. In addition, some elementsand/or features may be combined to configure an embodiment of thepresent invention. The sequence of the operations discussed in theembodiments of the present invention may be changed. Some elements orfeatures of one embodiment may also be included in another embodiment,or may be replaced by corresponding elements or features of anotherembodiment.

Embodiments of the present invention will be described, focusing on adata communication relationship between a base station and a terminal.The base station serves as a terminal node of a network over which thebase station directly communicates with the terminal Specific operationsillustrated as being conducted by the base station in this specificationmay also be conducted by an upper node of the base station, asnecessary.

In other words, it will be obvious that various operations allowing forcommunication with the terminal in a network composed of several networknodes including the base station can be conducted by the base station ornetwork nodes other than the base station. The term “base station (BS)”may be replaced with terms such as “fixed station,” “Node-B,” “eNode-B(eNB),” and “access point”. The term “relay” may be replaced with suchterms as “relay node (RN)” and “relay station (RS)”. The term “terminal”may also be replaced with such terms as “user equipment (UE),” “a mobilestation (MS),” “mobile subscriber station (MSS)” and “subscriber station(SS)”.

It should be noted that specific terms disclosed in the presentinvention are proposed for convenience of description and betterunderstanding of the present invention, and these specific terms may bechanged to other formats within the technical scope or spirit of thepresent invention.

In some cases, known structures and devices may be omitted or blockdiagrams illustrating only key functions of the structures and devicesmay be provided, so as not to obscure the concept of the presentinvention. The same reference numbers will be used throughout thisspecification to refer to the same or like parts.

Exemplary embodiments of the present invention are supported by standarddocuments disclosed for at least one of wireless access systemsincluding an institute of electrical and electronics engineers (IEEE)802 system, a 3rd generation partnership project (3GPP) system, a 3GPPlong term evolution (LTE) system, an LTE-advanced (LTE-A) system, and a3GPP2 system. In particular, steps or parts, which are not described inthe embodiments of the present invention to prevent obscuring thetechnical spirit of the present invention, may be supported by the abovedocuments. All terms used herein may be supported by the above-mentioneddocuments.

The embodiments of the present invention described below can be appliedto a variety of wireless access technologies such as code divisionmultiple access (CDMA), frequency division multiple access (FDMA), timedivision multiple access (TDMA), orthogonal frequency division multipleaccess (OFDMA), and single carrier frequency division multiple access(SC-FDMA). CDMA may be embodied through wireless technologies such asuniversal terrestrial radio access (UTRA) or CDMA2000. TDMA may beembodied through wireless technologies such as global system for mobilecommunication (GSM)/general packet radio service (GPRS)/enhanced datarates for GSM evolution (EDGE). OFDMA may be embodied through wirelesstechnologies such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802-20, and evolved UTRA (E-UTRA). UTRA is a part of universal mobiletelecommunications system (UMTS). 3rd generation partnership project(3GPP) long term evolution (LTE) is a part of evolved UMTS (E-UMTS),which uses E-UTRA. 3GPP LTE employs OFDMA for downlink and employsSC-FDMA for uplink. LTE-Advanced (LTE-A) is an evolved version of 3GPPLTE. WiMAX can be explained by IEEE 802.16e (wirelessMAN-OFDMA referencesystem) and advanced IEEE 802.16m (wirelessMAN-OFDMA advanced system).For clarity, the following description focuses on 3GPP LTE and 3GPPLTE-A systems. However, the spirit of the present invention is notlimited thereto.

LTE/LTE-A Resource Structure/Channel

Hereinafter, a radio frame structure will be described with reference toFIG. 1.

In a cellular OFDM wireless packet communication system, an uplink(UL)/downlink (DL) data packet is transmitted on a subframe basis, andone subframe is defined as a predetermined time interval including aplurality of OFDM symbols. 3GPP LTE standard supports a type-1 radioframe structure applicable to frequency division duplex (FDD) and atype-2 radio frame structure applicable to time division duplex (TDD).

FIG. 1(a) illustrates the type-1 radio frame structure. A downlink radioframe is divided into ten subframes. Each subframe includes two slots inthe time domain. The time taken to transmit one subframe is defined as atransmission time interval (TTI). For example, a subframe may have aduration of 1 ms and one slot may have a duration of 0.5 ms. A slot mayinclude a plurality of OFDM symbols in the time domain and includes aplurality of resource blocks (RBs) in the frequency domain. Since 3GPPLTE adopts OFDMA for downlink, an OFDM symbol represents one symbolperiod. An OFDM symbol may be referred to as an SC-FDMA symbol or asymbol period. A resource block (RB), which is a resource allocationunit, may include a plurality of consecutive subcarriers in a slot.

The number of OFDM symbols included in one slot depends on theconfiguration of a cyclic prefix (CP). CPs are divided into an extendedCP and a normal CP. For a normal CP configuring each OFDM symbol, a slotmay include 7 OFDM symbols. For an extended CP configuring each OFDMsymbol, the duration of each OFDM symbol extends and thus the number ofOFDM symbols included in a slot is smaller than in the case of thenormal CP. For the extended CP, a slot may include, for example, 6 OFDMsymbols. When a channel status is unstable as in the case of high speedmovement of a UE, the extended CP may be used to reduce inter-symbolinterference.

When the normal CP is used, each slot includes 7 OFDM symbols, and thuseach subframe includes 14 OFDM symbols. In this case, the first two orthree OFDM symbols of each subframe may be allocated to a physicaldownlink control channel (PDCCH) and the other three OFDM symbols may beallocated to a physical downlink shared channel (PDSCH).

FIG. 1(b) illustrates the type-2 radio frame structure. The type-2 radioframe includes two half frames, each of which has 5 subframes, adownlink pilot time slot (DwPTS), a guard period (GP), and an uplinkpilot time slot (UpPTS). Each subframe includes two slots. The DwPTS isused for initial cell search, synchronization, or channel estimation ina UE, whereas the UpPTS is used for channel estimation in an eNB and ULtransmission synchronization in a UE. The GP is provided to eliminateinterference taking place in UL due to multipath delay of a DL signalbetween DL and UL. Regardless of the type of a radio frame, a subframeof the radio frame includes two slots.

Herein, the illustrated radio frame structures are merely examples, andvarious modifications may be made to the number of subframes included ina radio frame, the number of slots included in a subframe, or the numberof symbols included in a slot.

FIG. 2 is a diagram illustrating a resource grid for one DL slot. A DLslot includes 7 OFDM symbols in the time domain and an RB includes 12subcarriers in the frequency domain. However, embodiments of the presentinvention are not limited thereto. For a normal CP, a slot may include 7OFDM symbols. For an extended CP, a slot may include 6 OFDM symbols.Each element in the resource grid is referred to as a resource element(RE). An RB includes 12 7 REs. The number NDL of RBs included in adownlink slot depends on a DL transmission bandwidth. A UL slot may havethe same structure as a DL slot.

FIG. 3 illustrates a DL subframe structure. Up to the first three OFDMsymbols of the first slot in a DL subframe used as a control region towhich control channels are allocated and the other OFDM symbols of theDL subframe are used as a data region to which a PDSCH is allocated. DLcontrol channels used in 3GPP LTE include, for example, a physicalcontrol format indicator channel (PCFICH), a physical downlink controlchannel (PDCCH), and a physical hybrid automatic repeat request (HARQ)indicator channel (PHICH). The PCFICH is transmitted at the first OFDMsymbol of a subframe, carrying information about the number of OFDMsymbols used for transmission of control channels in the subframe. ThePHICH carries a HARQ ACK/NACK signal in response to uplink transmission.Control information carried on the PDCCH is called downlink controlinformation (DCI). The DCI includes UL or DL scheduling information orUL transmission power control commands for UE groups. The PDCCH deliversinformation about resource allocation and a transport format for a DLshared channel (DL-SCH), resource allocation information about an ULshared channel (UL-SCH), paging information of a paging channel (PCH),system information on the DL-SCH, information about resource allocationfor a higher-layer control message such as a random access responsetransmitted on the PDSCH, a set of transmission power control commandsfor individual UEs of a UE group, transmission power controlinformation, and voice over internet protocol (VoIP) activationinformation. A plurality of PDCCHs may be transmitted in the controlregion. A UE may monitor a plurality of PDCCHs. A PDCCH is formed byaggregating one or more consecutive control channel elements (CCEs). ACCE is a logical allocation unit used to provide a PDCCH at a codingrate based on the state of a radio channel. A CCE corresponds to aplurality of RE groups. The format of a PDCCH and the number ofavailable bits for the PDCCH are determined depending on the correlationbetween the number of CCEs and a coding rate provided by the CCEs. AneNB determines the PDCCH format according to DCI transmitted to a UE andadds a cyclic redundancy check (CRC) to the control information. The CRCis masked by an identifier (ID) known as a radio network temporaryidentifier (RNTI) according to the owner or usage of the PDCCH. If thePDCCH is directed to a specific UE, its CRC may be masked by a cell-RNTI(C-RNTI) of the UE. If the PDCCH is for a paging message, the CRC of thePDCCH may be masked by a paging indicator identifier (P-RNTI). If thePDCCH delivers system information, particularly, a system informationblock (SIB), the CRC thereof may be masked by a system information IDand a system information RNTI (SI-RNTI). To indicate that the PDCCHdelivers a random access response in response to a random accesspreamble transmitted by a UE, the CRC thereof may be masked by a randomaccess-RNTI (RA-RNTI).

FIG. 4 illustrates a UL subframe structure. A UL subframe may be dividedinto a control region and a data region in the frequency domain. Aphysical uplink control channel (PUCCH) carrying uplink controlinformation is allocated to the control region and a physical uplinkshared channel (PUSCH) carrying user data is allocated to the dataregion. To maintain single carrier property, a UE does notsimultaneously transmit a PUSCH and a PUCCH. A PUCCH for a UE isallocated to an RB pair in a subframe. The RBs of the RB pair occupydifferent subcarriers in two slots. This is often called frequencyhopping of the RB pair allocated to the PUCCH over a slot boundary.

Synchronization Acquisition of D2D UE

Now, a description will be given of synchronization acquisition betweenUEs in D2D communication based on the foregoing description in thecontext of the legacy LTE/LTE-A system. In an OFDM system, iftime/frequency synchronization is not acquired, the resulting Inter-CellInterference (ICI) may make it impossible to multiplex different UEs inan OFDM signal. If each individual D2D UE acquires synchronization bytransmitting and receiving a synchronization signal directly, this isinefficient. In a distributed node system such as a D2D communicationsystem, therefore, a specific node may transmit a representativesynchronization signal and the other UEs may acquire synchronizationusing the representative synchronization signal. In other words, somenodes (which may be an eNB, a UE, and a Synchronization Reference Node(SRN, also referred to as a synchronization source)) may transmit a D2DSynchronization Signal (D2DSS) and the remaining UEs may transmit andreceive signals in synchronization with the D2DSS.

D2DSSs may include a Primary D2DSS (PD2DSS) or a Primary SidelinkSynchronization Signal (PSSS) and a Secondary D2DSS (SD2DSS) or aSecondary Sidelink Synchronization Signal (SSSS). The PD2DSS may beconfigured to have a similar/modified/repeated structure of a Zadoff-chusequence of a predetermined length or a Primary Synchronization Signal(PSS), and the SD2DSS may be configured to have asimilar/modified/repeated structure of an M-sequence or a SecondarySynchronization Signal (SSS). If UEs synchronize their timing with aneNB, the eNB serves as an SRN and the D2DSS is a PSS/SSS. A Physical D2DSynchronization Channel (PD2DSCH) may be a (broadcast) channel carryingbasic (system) information that a UE should first obtain before D2Dsignal transmission and reception (e.g., D2DSS-related information, aDuplex Mode (DM), a TDD UL/DL configuration, a resource pool-relatedinformation, the type of an application related to the D2DSS, etc.). ThePD2DSCH may be transmitted in the same subframe as the D2DSS or in asubframe subsequent to the frame carrying the D2DSS.

The SRN may be a node that transmits a D2DSS and a PD2DSCH. The D2DSSmay be a specific sequence and the PD2DSCH may be a sequencerepresenting specific information or a codeword produced bypredetermined channel coding. The SRN may be an eNB or a specific D2DUE. In the case of partial network coverage or out of network coverage,the SRN may be a UE.

In a situation illustrated in FIG. 5, a D2DSS may be relayed for D2Dcommunication with an out-of-coverage UE. The D2DSS may be relayed overmultiple hops. The following description is given with the appreciationthat relay of an SS covers transmission of a D2DSS in a separate formataccording to a SS reception time as well as direct Amplify-and-Forward(AF)-relay of an SS transmitted by an eNB. As the D2DSS is relayed, anin-coverage UE may communicate directly with an out-of-coverage UE. FIG.5 illustrates an exemplary case in which a D2DSS is relayed andcommunication is conducted between D2D UEs based on the relayed D2DSS.

A Time Resource Pattern (TRP) for use in transmitting data, a discoverysignal, etc. by a UE will be described according to various embodimentsof the present invention. The term ‘TRP’ may be interchangeably usedwith ‘Resource Pattern for Transmission (RPT)’ or ‘Time-RPT (T-RPT)’.However, the terms should not be construed as limiting the scope of thepresent invention. Thus, it is clarified that a resource pattern havingTRP properties as described below corresponds to a TRP. In the followingdescription, a scheme for indicating the position of transmissionresources by an eNB/UE is referred to as mode 1/type 2 and a scheme forindicating the position of transmission resources in a specific resourcepool by a transmitting UE (by the UE's selection) is referred to as mode2/type 1. In the following description, Scheduling Assignment (SA) maymean control information related to D2D data transmission and a channelcarrying the control information. Before data transmission, an SA mayfirst be transmitted. A receiving D2D UE may determine the position ofresources carrying the data by decoding the SA and then receive a D2Dsignal in the resources. In the following description, D2D may bereferred to as sidelink. For the convenience of description, the term‘TRP indication bit sequence’ may be used. The TRP indication bitsequence may include only an ID included in an SA. If the SA includes anadditional bit field indicating a TRP, the TRP indication bit sequencemay be interpreted as ID+TRP bit sequence. Or a bit sequence forindicating a TRP independent of the ID may be included in the SA. Inthis case, the TRP bit sequence may be interpreted as the TRP indicationbit sequence. A set of bit sequences used to indicate a TRP, includedand transmitted in the SA may be interpreted as the TRP indication bitsequence.

TRP

FIG. 6 illustrates TRPs according to an embodiment of the presentinvention. Referring to FIG. 6, a plurality of subframes 601 may includesubframes available for D2D signal transmission and reception (e.g., ULsubframes in TDD, and D2D communication subframes in FIG. 6) andsubframes unavailable for D2D signal transmission and reception (non-D2Dcommunication subframes in FIG. 6). The plurality of subframes 601 maybe included within a D2D control information transmission period (e.g.,a physical sidelink control channel). A subframe pool 602 for datatransmission may be determined, which includes only D2D communicationsubframes from among the plurality of subframes 601.

As TRPs (TRP #0, #1, . . . ) are applied to the subframe pool 602 fordata transmission, a set of subframes to transmit D2D data may bedetermined. For example, if TRP #1 is applied to the subframe pool 602for data transmission, an 8^(th) subframe and 10^(th) to 16^(th)subframes may be included in a subframe set, for D2D data transmission.Shaded parts of the TRPs in FIG. 16 may indicate subframes that willcarry D2D data. A TRP may be a bitmap having bits corresponding to therespective subframes of a subframe pool for data transmission. If a bitof the bitmap is set to 1, the bit may indicate a subframe to transmitD2D data. Specifically, if a TRP is configured to be a bitmap, theshaded parts of the TRP may be 1s and the non-shaded parts of the TRPmay be 0s in FIG. 6. For example, TRP #1 is a bitmap of {0, 0, 0, 0, 0,0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1}.

Once a subframe set is determined for transmission of D2D data, the D2Ddata may be transmitted in the subframe set. Upon receipt of an SA, a UEmay detect and decode a D2D signal in corresponding subframes, expectingtransmission of the D2D signal in the subframes.

In the above description, a Transport Block (TB) for D2D data may betransmitted in a predetermined number of subframes in a subframe set.That is, the number of repetitions/a retransmission number/the number ofretransmissions may be predetermined for each TB. For example, thenumber of retransmissions per TB may be fixed to 4.

The above-described plurality of subframes may be contiguous subframesfollowing D2D control information-related subframes (including ULsubframes that may carry D2D control information, DL subframes with norelation to the UL subframes, and special subframes in TDD) in one D2Dcontrol information period (i.e., one SA period). The D2D controlinformation (an SA, an MCS, resource allocation information, a TRP,etc.) may be transmitted in subframes determined to transmit D2D controlinformation (i.e., a subframe pool (for D2D control information)) fromamong subframes available for transmission of D2D control informationaccording to an SA subframe bitmap. In this case, information indicatinga TRP in a subframe next to the subframe pool for D2D controlinformation may be transmitted in the D2D control information. If one SAperiod is configured as described above, subframes included in asubframe pool for data transmission are not overlapped with subframesincluded in a subframe pool for D2D control information. Morespecifically, if the subframe pool for D2D control information isoverlapped with the subframe pool for D2D data transmission, it may beregulated that D2D control information or D2D data is always transmittedand the D2D control information and the D2D data are not transmitted inthe same subframe.

Meanwhile, the subframe pool for data transmission may not be definedseparately in D2D communication mode 1. In this case, UL subframesfollowing the subframe pool for D2D control information transmission(specifically, a subframe pool including the first subframe of asubframe bitmap for D2D control information transmission to a subframecorresponding to the last 1 of the bitmap) may be a subframe pool forimplicit mode 1 D2D data transmission.

Application of TRP

In the foregoing description, a TRP may be applied to subframes asfollows.

A UE may determine a subframe indicator bitmap corresponding to TRPindication information. If the UE is a D2D control informationtransmitter, the TRP indication information may be transmitted in D2Dcontrol information. If the UE is a D2D control information receiver,the TRP indication information may be included in received D2D controlinformation. Herein, the TRP indication information may be described ina later-described TRP indication part or may be an index indicating aspecific subframe indicator bitmap. For example, if the size of thesubframe indicator bitmap is 8, there may be a set of available bitmaps.An index may be assigned to each bitmap included in the bitmap set and asubframe indicator bitmap may be determined by such as index.

A bitmap to be applied to a subframe pool for data transmission may bedetermined from the subframe indicator bitmap. The subframe indicatorbitmap may be smaller than the subframe pool for data transmission insize. In this case, the subframe indicator bitmap (e.g., a TRPindication bit sequence) may be repeated. If the length of the TRPindication bit sequence is M, the M-bit sequence is simply repeated andfilled in the remaining L subframes. If L is not a multiple of M, a TRPmay be generated by sequentially filling the remaining bit sequence inthe L subframes.

That is, if the subframe indicator bitmap is smaller in size than thesubframe pool for data transmission, the subframe indicator bitmap maybe repeated within the bitmap for the subframe pool for datatransmission.

For example, if the size M of the subframe indicator bitmap is smallerthan the number of subframes in the resource pool for data transmissionand the UE transmits D2D data in the first subframe of the subframe poolfor data transmission, the UE may transmit D2D data in a (1+M)^(th)subframe of the subframe pool. Or a first bit value of the bitmap (to beapplied to the subframe pool for data transmission) may be equal to a(subframe indicator bitmap size+1)^(th) bit value.

If the size of the subframe pool for data transmission is not a multipleof the size of the subframe indicator bitmap, the bits of the lastrepeated subframe indicator bitmap may be used sequentially. In otherwords, if the size of the subframe pool for data transmission is not amultiple of the size of the subframe indicator bitmap, the last repeatedsubframe indicator bitmap may be truncated. Specifically, if thesubframe indicator bitmap is 16 bits {0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1,1, 1, 1, 1, 1} and the subframe pool includes 36 subframes, the bitmap(to be applied to a subframe pool for data transmission) is configuredby repeating the subframe indicator bitmap twice and using the first 4bits of the subframe indicator bitmap sequentially at the thirdrepetition (while truncating the remaining bits). That is, the bitmap(to be applied to the subframe pool for data transmission) is {0, 0, 0,0, 0, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1,1, 1, 1, 1, 1, 0, 0, 0, 0}.

Indication of TRP

Now, a description will be given of a method for indicating theabove-described TRP.

First, an eNB may indicate an ID and TRP bits included and transmittedin an SA by a D2D SA grant in mode 1. The ID sequence included in the SAand/or the sequence of a TRP bit field included in the SA (a bit fieldindicating a specific ID and/or a TRP) may be explicitly included in theD2D SA grant. Or the ID sequence to be transmitted in the SA and/or theTRP bit field to be transmitted in the SA may be generated by hashingthe bit sequence of a D2D-RNTI or using partial bits (e.g., lower Nbits) of the bit sequence of the D2D-RNTI. Because an RNTI is differentfor each UE and at least a part of the RNTI is used, the position of D2Dresources may be configured for each UE without additional signaling. AD2D-RNTI is an ID pre-signaled to distinguish D2D control informationfrom other control information and is used for masking the CRC of theD2D control information. A part of the ID included and transmitted inthe SA may be generated from the RNTI and the remaining part of the IDmay be generated based on a target ID (or a group ID). Or the ID may begenerated by combining (e.g., AND/XOR/OR-operating) both the RNTI andthe target or group ID. The ID included and transmitted in the SA may bechanged over time. Characteristically, only a Transmission (Tx) UE IDmay be changed. This is because if up to a target UE ID part is hoppedand a target UE is not aware of the hopping, the target UE may notdetect the ID. If the target UE is aware of even a hopping pattern ofthe target UE ID part, every ID sequence included in the SA may behopped in a predetermined rule. The changeability (hopping) of the IDsequence over time may be implemented by directly setting a differentbit field in a D2D SA grant by the eNB and the ID sequence may bechanged in a predetermined rule after the D2D SA grant of the eNB. Forexample, the ID sequence included in the D2D SA grant may be used as aninitialization parameter for a random sequence and a time-variantsequence may be generated using a random sequence created using theinitialization parameter.

Second, an ID may be transmitted in an SA and a TRP may be determinedusing the ID in mode 2. The ID may be a short ID induced from an ID (atransmission and/or reception (target or group) ID) by a higher layer ora bit sequence used to configure the transmission position of data and ascrambling parameter. If the ID included in the SA is too short forcreation of TRP candidates, the probability of collision between IDs isincreased. In this case, a plurality of Tx UEs are likely to use thesame TRP. To prevent this, a part of the bits of the SA may include bitsindicating a TRP. Also, a specific TRP may be indicated by combining anID bit field and bits of a TRP field in the SA. For example, the IDincluded in the SA may be used to indicate a TRP set and TRP indicationbits included in the SA may indicate a specific index within the TRPset. In another example, the TRP bits included in the SA may indicate aspecific TRP set within a resource pool and the ID included in the SAmay indicate a specific TRP within the pool/set indicated by the TRPbits. In this case, the bits indicating a TRP set may be transmittedsemi-statically without being transmitted in every SA. For example, thebits indicating a TRP set may be used as a virtual CRC on the assumptionthat the bits are transmitted in every n^(th) SA or even though the bitsare transmitted in every SA, they are not changed over n SAtransmissions. Meanwhile, these TRP bits are not included additionally.Rather, the TRP bits may be transmitted by borrowing an unused state ofMCS bits or any other SA bit field. Or a TRP pattern may be indicated byusing all unused states of additionally included bits and other bitfields.

Meanwhile, the size of TRP bits used in an indication of an SA may bechanged according to the size of a D2D UE group or the number of Tx UEsin the group. For example, if a specific police officer group includes Npolice officers, the number of TRP indication bits is set to log 2(N).Herein, the remaining unused bits may be used for other purposes or maybe set to 0s for use as a virtual CRC.

Meanwhile, an ID may be set differently for a TRP in mode 1 and mode 2.For example, while a TRP may be indicated using only a Tx UE ID in mode1, a TRP may be indicated using both a Tx UE ID and a target UE ID(group ID) in mode 2.

To configure a TRP, the following information may be used: i)information about the size of a transmission opportunity from theviewpoint of a UE (this information indicates how many resources areallocated to one UE by one SA); and ii) information about the number ofretransmissions for each TB (this information may be information aboutthe number of TBs transmitted during one SA period. In this case, thenumber of retransmissions for each TB may be calculated by flooring thesize (number) of transmission opportunities during one SA period/thenumber of TBs transmitted by one SA. Or this information may beinformation about the (maximum) number of repetitions for each TB). Partof the information may be preset or configured by the network. Theinformation may be preset for an out-of-coverage UE or signaled to theout-of-coverage UE from another UE within the network by aphysical-layer signal or a higher-layer signal. In addition, part of theinformation may be included and transmitted in an SA. For example, thetransmission opportunity size may be preset or configured by thenetwork. Herein, a retransmission number for each TB may be included andtransmitted in the SA. On the other hand, information about thetransmission opportunity size may be included and transmitted in the SAand information about the retransmission number may be preset orsemi-statically indicated in a higher-layer signal by the network.

In a specific example, if an SA includes an 8-bit ID, the number of TRPsdistinguishable by IDs is 256 (=2^8). If a mode-2 resource pool includes16 subframes and a transmission opportunity size is 8, the number ofTRPs that can be generated is 12870 (=16C8). Therefore, it is impossibleto identify a TRP only by the ID bits included in the SA. To avoid thisproblem, additional bits may be included in the SA in order to indicatea TRP in the above-described method. In this case, about 6 additionalbits are needed to distinguish all TRPs that can be produced. Theadditional bits may be available from a combination of unused MCS statesand a new bit field or from an additional bit field.

Signaling of TRP Subset

The network may signal a TRP subset configuration by a higher-layersignal (e.g., an RRC signal). More specifically, a UE may determine abitmap for application to a subframe pool for data transmission usingTRP indication information and transmit D2D data in subframes indicatedby the bitmap, as described before. In the case where an RRC InformationElement (IE) related to a TRP subset is configured for the UE, if the UEis not related to the RRC IE related to a TRP subset, a set of bitmapsthat can be indicated by the TRP indication information may be a subsetof a bitmap set that can be indicated by the TRP indication information.Herein, the TRP indication information is an index indicating one bitmap in a bitmap set.

The above description will be detailed with reference to [Table 1]below. [Table 1] defines a relationship between TRP indicationinformation I_(TRP) and a bitmap corresponding to the TRP indicationinformation I_(TRP), under the condition that the size of a TRP-relatedsubframe indicator bitmap is 6. For example, if the TRP indicationinformation I_(TRP) is 22, the subframe indicator bitmap is {0, 1, 1, 0,1, 0}.

TABLE 1 I_(TRP) k_(TRP) (b′₀, b′₁, . . . b′_(N) _(TRP) ⁻¹) 0 reservedreserved 1 1 (1, 0, 0, 0, 0, 0) 2 1 (0, 1, 0, 0, 0, 0) 3 2 (1, 1, 0, 0,0, 0) 4 1 (0, 0, 1, 0, 0, 0) 5 2 (1, 0, 1, 0, 0, 0) 6 2 (0, 1, 1, 0, 0,0) 7 3 (1, 1, 1, 0, 0, 0) 8 1 (0, 0, 0, 1, 0, 0) 9 2 (1, 0, 0, 1, 0, 0)10 2 (0, 1, 0, 1, 0, 0) 11 3 (1, 1, 0, 1, 0, 0) 12 2 (0, 0, 1, 1, 0, 0)13 3 (1, 0, 1, 1, 0, 0) 14 3 (0, 1, 1, 1, 0, 0) 15 4 (1, 1, 1, 1, 0, 0)16 1 (0, 0, 0, 0, 1, 0) 17 2 (1, 0, 0, 0, 1, 0) 18 2 (0, 1, 0, 0, 1, 0)19 3 (1, 1, 0, 0, 1, 0) 20 2 (0, 0, 1, 0, 1, 0) 21 3 (1, 0, 1, 0, 1, 0)22 3 (0, 1, 1, 0, 1, 0) 23 4 (1, 1, 1, 0, 1, 0) 24 2 (0, 0, 0, 1, 1, 0)25 3 (1, 0, 0, 1, 1, 0) 26 3 (0, 1, 0, 1, 1, 0) 27 4 (1, 1, 0, 1, 1, 0)28 3 (0, 0, 1, 1, 1, 0) 29 4 (1, 0, 1, 1, 1, 0) 30 4 (0, 1, 1, 1, 1, 0)31 5 (1, 1, 1, 1, 1, 0) 32 1 (0, 0, 0, 0, 0, 1) 33 2 (1, 0, 0, 0, 0, 1)34 2 (0, 1, 0, 0, 0, 1) 35 3 (1, 1, 0, 0, 0, 1) 36 2 (0, 0, 1, 0, 0, 1)37 3 (1, 0, 1, 0, 0, 1) 38 3 (0, 1, 1, 0, 0, 1) 39 4 (1, 1, 1, 0, 0, 1)40 2 (0, 0, 0, 1, 0, 1) 41 3 (1, 0, 0, 1, 0, 1) 42 3 (0, 1, 0, 1, 0, 1)43 4 (1, 1, 0, 1, 0, 1) 44 3 (0, 0, 1, 1, 0, 1) 45 4 (1, 0, 1, 1, 0, 1)46 4 (0, 1, 1, 1, 0, 1) 47 5 (1, 1, 1, 1, 0, 1) 48 2 (0, 0, 0, 0, 1, 1)49 3 (1, 0, 0, 0, 1, 1) 50 3 (0, 1, 0, 0, 1, 1) 51 4 (1, 1, 0, 0, 1, 1)52 3 (0, 0, 1, 0, 1, 1) 53 4 (1, 0, 1, 0, 1, 1) 54 4 (0, 1, 1, 0, 1, 1)55 5 (1, 1, 1, 0, 1, 1) 56 3 (0, 0, 0, 1, 1, 1) 57 4 (1, 0, 0, 1, 1, 1)58 4 (0, 1, 0, 1, 1, 1) 59 5 (1, 1, 0, 1, 1, 1) 60 4 (0, 0, 1, 1, 1, 1)61 5 (1, 0, 1, 1, 1, 1) 62 5 (0, 1, 1, 1, 1, 1) 63 6 (1, 1, 1, 1, 1, 1)64-127 reserved reserved

The above [Table 1] may be referred to as a mother bitmap set that isavailable, if there is no specific RRC signaling. In this case, an RRCIE related to a TRP subset may be configured for a UE. The RRC IErelated to a TRP subset may impose a restriction on an index-basedavailable set. For example, if k_(TRP) available to the UE is 4 atmaximum in [Table 1] and the TRP subset-related RRC IE is {1, 1, 1, 0},a set of bitmaps corresponding to k_(TRP) values of 1, 2, and 3 may be asubset of the mother bitmap set. That is, in the case where a TRPsubset-related IE is configured by RRC signaling, if the UE is notrelated to the TRP set-related RRC IE (if the RRC IE is not signaled orif the RRC IE is signaled but not configured), a set of bitmapsavailable to the UE or a set of TRP indication information may be asubset of a set of bitmaps or TRP indication information.

The TRP subset-related RRC IE may be for a mode-2 UE.

Restricting a TRP subset by the network may be effective especially whena UE determines transmission resources as in mode 2. In the case wherethe UE selects a TRP index randomly, if there are a small number ofneighbor UEs and thus interference is not severe, the UE may transmit apacket faster by selecting a large k_(TRP) value. On the other hand, ifthere are a large number of neighbor UEs and thus interference issevere, the UE may be limited to a relatively small k_(TRP) valuethrough a subset to solve inband emission and half duplexing.Consequently, the specific UE may be prevented from causing severeinterference continuously.

Meanwhile, although a TRP subset may be restricted by restrictingk_(TRP) values, it may be restricted by restricting specific TRPindexes. For example, use of a specific I_(TRP) set may be signaled to aspecific UE or UE group. Despite a requirement for more signaling bitsthan in the case of restricting a subset by signaling a k_(TRP) value,this method enables more flexible TRP subset restriction. Also, thismethod may be used to make a UE or UE group different from a specific UEor UE group use a different subframe in the time domain. For example, aTRP subset may be configured for UE group A so that UE group A mayperform transmission in all or a part of the first 4 subframes of a TRPbitmap, whereas a TRP subset may be configured for UE group B so that UEgroup B may perform transmission in all or a part of the last 4subframes of the TRP bitmap.

Determination of Set of Values Available as k

A set of values available as k (k_(TRP) or M1) being the number of 1s ina subframe indicator bitmap may be determined, as follows.

Embodiment 1

A set of values available as the number k of 1in a subframe indicatorbitmap may vary depending on a UL/DL configuration set to which a UL/DLconfiguration configured for a UE belongs. In consideration of the UL/DLconfigurations illustrated in [Table 2] and the numbers of HARQprocesses illustrated in [Table 3], the size of a subframe indicatorbitmap may be 8 for UL/DL configurations 1, 2, 4, and 5, 7 for UL/DLconfiguration 0, and 6 for UL/DL configurations 3 and 6. This is done toallocate D2D data subframes according to the number of UL HARQ processesin TDD.

TABLE 2 Downlink-to- Uplink- Uplink downlink Switch-point subframenumber # of UL configuration periodicity 0 1 2 3 4 5 6 7 8 9 subframe 05 ms D S U U U D S U U U 6 1 5 ms D S U U D D S U U D 4 2 5 ms D S U D DD S U D D 2 3 10 ms D S U U U D D D D D 3 4 10 ms D S U U D D D D D D 25 10 ms D S U D D D D D D D 1 6 5 ms D S U U U D S U U D 5

TABLE 3 Number of HARQ Number of HARQ TDD UL/DL processes for normalprocesses for subframe configuration HARQ operation bundling operation 07 3 1 4 2 2 2 N/A 3 3 N/A 4 2 N/A 5 1 N/A 6 6 3

If a set of UL/DL configurations is configured in this manner, a set ofvalues available as k may be configured for each UL/DL configuration.For example, if one of UL/DL configurations 1, 2, 4, and 5 is configuredfor a UE, a set of values available as k may be {1, 2, 4, 8}. If UL/DLconfiguration 0 is configured for the UE, the set of values available ask may be {1, 2, 3, 4, 5, 6, 7}. If one of UL/DL configurations 3 and 6is configured for the UE, the set of values available as k may be {1, 2,3, 4, 5, 6} (the size of the set of values available as k may be largestin a UL/DL configuration having the most UL subframes). Theseconfigurations may be for transmission mode 1.

The reason that the value available as k is set differently according tothe TDD UL/DL configuration is that the number of subframe is differentaccording to the TDD UL/DL configuration and latency in case of usingsame k may be different according to the TDD UL/DL configuration. Tosolve this problem, it is needed to reduce available latency by usinghigh value of k when TDD UL/DL configuration has a fewer number of ULsubframe.

Embodiment 2

A set of values available as k being the number of 1s in a subframeindicator bitmap may set differently depending on modes. In other words,if a transmission mode is changed, a set of values available as k beingthe number of 1s in a subframe indicator bitmap may be changed eventhough a UL/DL configuration configured for a UE is not changed.

Specifically, if the UE operates in transmission mode 2 and one of UL/DLconfigurations 1, 2, 4, and 5 is configured for the UE (or the duplexmode of the UE is Frequency Division Duplex (FDD)), the set of valuesavailable as k may be {1, 2, 4}. If the UE operates in transmission mode2 and UL/DL configuration 0 is configured for the UE, the set of valuesavailable as k may be {1, 2, 3, 4, 5}. If the UE operates intransmission mode 2 and one of UL/DL configurations 3 and 6 isconfigured for the UE, the set of values available as k may be {1, 2, 3,4}. Or the set of values available as k may be smaller in transmissionmode 2 than in transmission mode 1 irrespective of the UL/DLconfiguration of the UE. Or the set of values available as k intransmission mode 2 may be a subset of the set of values available as kin transmission mode 1.

In summary, different subframe indicator bitmap sizes N and/or differentk combinations may be used for mode 1 and mode 2. This is done not touse heavy k values (in other words, k values that make k/N ratiosapproximate to 1) intentionally in order to overcome the half duplexconstraint. If a specific UE uses a heavy k values in mode 2, the otherUEs may cause severe inband radiation interference in most subframe dueto transmission of the specific UE. Accordingly, it is preferred torestrict the maximum value of k to or below a predetermined value inmode 2. In addition, to solve the half-duplex constraint in mode 2, itis preferred to set k to be close to a half of N in terms ofmaximization of the number of available combinations and solving thehalf-duplex constraint. For example, if N is 6, a k set includes 3.

Embodiment 3-1

A set of values available as k being the number of 1s in a subframeindicator bitmap may be configured for each duplex mode. A set ofsubframe indicator bitmaps (of size N) may be predefined and an entireTRP may be configured within a subframe pool by repeating a subframeindicator bitmap of length N. Herein, a set of k values (k is the numberof 1s transmittable in a subframe indicator bitmap) may be predeterminedEach subframe indicator bitmap of the set may be indexed and a specificindex may be indicated by TRP indication bits of an SA. For example, N=8and k={1, 2, 4, 8}. More specifically, a set of subframe indicatorbitmaps may be defined for possible k values. If the size of the set islarger than the number of bits of a subframe indicator bitmap that canbe indicated by an SA, some subframe indicator bitmaps may be selected.Otherwise, all possible combinations that can be produced according to(N, k) may be included in the set of subframe indicator bitmaps. Forexample, if an SA indicates a subframe indicator bitmap using 8 bits, itmay indicate a total of 256 subframe indicator bitmaps. If one bit outof the eight bits is used to identify a set of subframe indicatorbitmaps, a total of 128 subframe indicator bitmaps may be indicated bythe SA. If N=8 and k={1, 2, 4, 8} as in the above example, a total of107 (=8C1+8C2+8C4+8C8) subframe indicator bitmaps may be defined. Asubframe indicator bitmap may be applied to UL subframes and only to aD2D resource pool within the UL subframes. Subframes are sparselyconfigured in the D2D resource pool in TDD, relative to FDD. For VoIPpackets having a delay constraint, a subframe indicator bitmap needs tobe designed for enabling more transmissions. In this case, a set of kvalues may be set differently for FDD and TDD. In TDD, allowing moretransmissions is preferable in that the delay constraint is satisfied.In this context, a k set may be configured mainly using large values inTDD, relative to FDD. For example, if N=8 and k={1, 2, 4, 8} in FDD, N=8and k={1, 4, 6, 8} in TDD. 2 in FDD is changed to 6 in TDD to therebyenable more transmissions in TDD without changing Hamming distancecharacteristics between TRPs.

If N=8, one of the combinations listed in [Table 4] may be selected. Thecombinations may be configured differently for each TDD configuration.For example, in the case of TDD configuration 5, a combination with alarger number of 1s is selected (e.g., {4, 6, 7, 8} in [Table 4]). Onthe other hand, if the number of UL subframes is large as in TDDconfiguration 0, a combination with a smaller number of 1s (e.g., {1, 4,6, 8} in [Table 4]) is used. In other words, a set of K values in FDDare equal to or larger than a set of K values in TDD. This combinationmay be preset according to an FDD/TDD configuration or signaled in aphysical-layer/higher-layer signal by the network irrespective of anFDD/TDD configuration.

TABLE 4 Total number Combination of subframe index k set Note indicatorbitmaps Sum(k) 0 1 2 4 8 Same as 107 15 in FDD 1 1 2 5 7 100 15 2 1 2 58 93 16 3 1 2 6 7 72 16 4 1 2 6 8 65 17 5 1 2 7 8 45 18 6 1 3 5 7 128 167 1 3 5 8 121 17 8 1 3 6 7 100 17 9 1 3 6 8 93 18 10 1 3 7 8 73 19 11 14 6 7 114 18 12 1 4 6 8 107 19 13 1 4 7 8 87 20 14 1 5 6 7 100 19 15 1 56 8 93 20 16 1 5 7 8 73 21 17 1 6 7 8 45 22 18 2 3 6 7 120 18 19 2 3 6 8113 19 20 2 3 7 8 93 20 21 2 4 6 8 127 20 22 2 4 7 8 107 21 23 2 5 6 7120 20 24 2 5 6 8 113 21 25 2 5 7 8 93 22 26 2 6 7 8 65 23 27 3 5 7 8121 23 28 3 6 7 8 93 24 29 4 6 7 8 107 25 30 5 6 7 8 93 26

Embodiment 3-2

A set of values available as k may not include a specific k valuedepending on TDD or FDD. For example, a k value of 1 may not be used inTDD configuration 5. If for N=8, k=1 and the number of transmissions is1 for each MAC PDU, a delay of at least 320 ms is required, exceeding a200-ms delay budget. If k=2, a 160-ms delay occurs, satisfying the200-ms delay budget. The same principle may be applied to other cases.For example, if a specific k value does not satisfy a VoIP delayconstraint in a specific TDD configuration, a UE may select a subframeindicator bitmap from among the remaining k values except for the kvalue. More generally, if the UE transmits a VoIP packet (or a (video)packet having a different delay constraint), it may be regulated thatthe UE does not use a subframe indicator bitmap that does not satisfythe delay constraint. For the convenience of description, a set ofsubframe indicator bitmaps that satisfy a delay constraint may bereferred to as a set of valid subframe indicator bitmaps. For example,it is assumed that a bitmap size of a resource pool is 4 and the lengthof a subframe indicator bitmap is 8 in TDD configuration 5. Since thelength of the resource pool is not equal to the length of the subframeindicator bitmap, the last 4 bits of the subframe indication bit may betruncated. If only the first 4 bits of the subframe indicator bitmap areused, even though the UE selects a large k value, 1s are located at thelast positions. Therefore, the UE may have no transmission opportunityin the first 4 bits. For example, if the UE selects 00001111, the UE mayhave no transmission opportunity in the above configuration. In thiscase, the VoIP delay constraint may be satisfied only when at least one1 is present in the first four bits of the subframe indicator bitmap.Therefore, it may be regulated that subframe indicator bitmap, thesubframe indicator bitmap may be a valid subframe indicator bitmap onlywhen the subframe indicator bitmap has at least one 1 in the first 4bits and that the UE selects a subframe indicator bitmap from a set ofvalid subframe indicator bitmaps.

To assign more transmission opportunities in TDD than in FDD, an N-kcombination having a larger k/N value may be used. For example, if N is8 and a maximum k set is {1, 2, 4, 8} in FDD, N=7 and k={1, 3, 5, 7} inTDD. A comparison between FDD and TDD in terms of k/N values revealsthat TDD uses larger k/N values, {0.1429, 0.4286, 0.7143, 1.0000} thank/N={0.125, 0.25, 0.5, 1} in FDD. This means that more transmissionopportunities are available in TDD. In summary, since UL subframes aremore sparse in TDD than in FDD, a higher k value or a higher k/N valuemay be used in TDD than in FDD.

[Table 5] and [Table 6] illustrate exemplary sets of values available ask based on the above descriptions.

TABLE 5 For mode 1 and/or Total number mode 2 N k of T-TRP TDDconfiguration 8 {2, 4, 6, 8} or {1, 2, 4, 8} 127 or 107 1, 2, 4, 5 TDDconfiguration 7 {2, 4, 6, 7} or {2, 3, 4, 7} or 64 or 92 or 0 {1, 2, 4,7} or {1, 2, 3, 4, 5, 64 or 127 6, 7} TDD configuration 6 {2, 4, 6} or{2, 3, 4, 6} or 31 or 51 or 3, 6 {1, 2, 3, 6} or {1, 2, 4, 6} or 42 or37 or 63 {1, 2, 3, 4, 5, 6}

TABLE 6 Total number For mode 2 N k of T-TRP TDD configuration 8 {1, 2,4} or {2, 4} or 106 or 98 or 1, 2, 4, 5 {2, 4, 6} or {3, 4} 126 or 126TDD configuration 7 {2, 3, 4} or {2, 4, 6} or 91 or 63 or 0 {1, 2, 4} or{1, 2, 3, 4}, 63 or 98 or {1, 2, 3, 4, 5}, {1, 2, 3, 4, 119 or 126 5, 6}TDD configuration 6 {2, 4} or {1, 2, 3} or 30 or 41 or 3, 6 {2, 3, 4} or{1, 2, 4} or 50 or 36 or {1, 2, 3, 4}, {1, 2, 3, 4, 5} 56 or 62

To describe [Table 5] and [Table 6] in greater detail, k is set in mode1 in such a manner that more transmission opportunities and moreavailable combinations may be given in TDD than in FDD. To overcome thehalf-duplex constraint, k equal to or close to a half weight (N/2) isincluded in mode 2. For example, since N is an odd number, 7 in TDDconfiguration 0, a k value of 3 or 4 may be included.

Meanwhile, if the number of bits that can be indicated by a T-TRP in anSA is limited, a set of k values is preferably set so that all ofcombinations that can be represented by the T-TRP bits in the SA may beused if possible. Particularly, as more patterns are used in D2Dresource allocation, interference randomization between UEs increasesand thus performance is improved. For example, if the number of bitsthat may indicate a TRP in an SA is 7, a total of 128 TRPs may bedistinguished and 128 sets of k values may all be used. Thus, theresulting increase in the interference randomization effect may lead toimproved performance.

Configurations of Apparatuses According to Embodiment of the PresentInvention

FIG. 7 is a block diagram of a transmission point and a UE according toan embodiment of the present invention.

Referring to FIG. 7, a transmission point 10 according to the presentinvention may include a Reception (Rx) module 11, a Tx module 12, aprocessor 13, a memory 14, and a plurality of antennas 15. Use of theplurality of antennas 15 means that the transmission point 10 supportsMIMO transmission and reception. The reception module 11 may receive ULsignals, data, and information from a UE. The Tx module 12 may transmitDL signals, data, and information to a UE. The processor 13 may provideoverall control to the transmission point 10.

The processor 13 of the transmission point 10 according to theembodiment of the present invention may perform necessary operations inthe afore-described embodiments.

Besides, the processor 13 of the transmission point 10 processesreceived information and information to be transmitted to the outside ofthe transmission point 10. The memory 14 may store the processedinformation for a predetermined time and may be replaced with acomponent such as a buffer (not shown).

Referring to FIG. 7 again, a UE 20 according to the present inventionmay include an Rx module 21, a Tx module 22, a processor 23, a memory24, and a plurality of antennas 25. Use of the plurality of antennas 25means that the UE 20 supports MIMO transmission and reception using theplurality of antennas 25. The Rx module 21 may receive DL signals, data,and information from an eNB. The Tx module 22 may transmit UL signals,data, and information to an eNB. The processor 23 may provide overallcontrol to the UE 20.

The processor 23 of the UE 20 according to the embodiment of the presentinvention may perform necessary operations in the afore-describedembodiments.

Besides, the processor 23 of the UE 20 processes received informationand information to be transmitted to the outside of the UE 20. Thememory 24 may store the processed information for a predetermined timeand may be replaced with a component such as a buffer (not shown).

The above transmission point and UE may be configured in such a mannerthat the above-described various embodiments of the present inventionmay be implemented independently or in combination of two or more. Aredundant description is omitted for clarity.

The description of the transmission point 10 in FIG. 7 is applicable toa relay as a DL transmitter or a UL receiver, and the description of theUE 20 in FIG. 7 is applicable to a relay as a DL receiver or a ULtransmitter.

As is apparent from the foregoing description, a delay and a half duplexproblem that should be considered in using a time resource pattern canbe solved according to an embodiment of the present invention.

The embodiments of the present invention may be implemented by variousmeans, for example, in hardware, firmware, software, or a combinationthereof.

In a hardware configuration, the method according to the embodiments ofthe present invention may be implemented by one or more ApplicationSpecific Integrated Circuits (ASICs), Digital Signal Processors (DSPs),Digital Signal Processing Devices (DSPDs), Programmable Logic Devices(PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers,microcontrollers, or microprocessors.

In a firmware or software configuration, the method according to theembodiments of the present invention may be implemented in the form ofmodules, procedures, functions, etc. performing the above-describedfunctions or operations. Software code may be stored in a memory unitand executed by a processor. The memory unit may be located at theinterior or exterior of the processor and may transmit and receive datato and from the processor via various known means.

The detailed description of the preferred embodiments of the presentinvention has been given to enable those skilled in the art to implementand practice the invention. Although the invention has been describedwith reference to the preferred embodiments, those skilled in the artwill appreciate that various modifications and variations can be made inthe present invention without departing from the spirit or scope of theinvention described in the appended claims. Accordingly, the inventionshould not be limited to the specific embodiments described herein, butshould be accorded the broadest scope consistent with the principles andnovel features disclosed herein.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein. It is obvious to those skilled in the art thatclaims that are not explicitly cited in each other in the appendedclaims may be presented in combination as an embodiment of the presentinvention or included as a new claim by a subsequent amendment after theapplication is filed.

INDUSTRIAL APPLICABILITY

The above-described embodiments of the present invention are applicableto various mobile communication systems.

What is claimed is:
 1. A method for transmitting Device-to-Device (D2D)data by a User Equipment (UE) in a wireless communication system, themethod comprising: determining a bitmap to be applied to a subframe poolfor data transmission from a subframe indicator bitmap; determining aset of suframes to transmit the D2D data by using the bitmap to thesubframe pool for data transmission; and transmitting the D2D data in asubframe included in the determined subframe set, wherein a set ofvalues available as k being the number of 1s in the subframe indicatorbitmap are determined according to a Uplink/Downlink (UL/DL)configuration set to which a UL/DL configuration configured for the UEbelongs, wherein the UL/DL configuration sets comprise UL/DLconfiguration 1, 2, 4 and 5, UL/DL configuration 0 and UL/DLconfigurations 3 and 6, and wherein a value of 1 in the subframeindicator bitmap indicates the subframe used to transmit the D2D data.2. The method according to claim 1, wherein if the UL/DL configurationconfigured for the UE is one of UL/DL configurations 1, 2, 4 and 5, theset of values available as k is {1, 2, 4, 8}.
 3. The method according toclaim 1, wherein if the UL/DL configuration configured for the UE isUL/DL configuration 0, the set of values available as k is {1, 2, 3, 4,5, 6, 7}.
 4. The method according to claim 1, wherein if the UL/DLconfiguration configured for the UE is one of UL/DL configurations 3 and6, the set of values available as k is {1, 2, 3, 4, 5, 6}.
 5. The methodaccording to claim 1, wherein the D2D data transmission is fortransmission mode
 1. 6. The method according to claim 1, wherein if theset of values available as k is {1, 2, 4, 8}, {1, 2, 3, 4, 5, 6, 7}, or{1, 2, 3, 4, 5, 6}, the size of the subframe indicator bitmap is 8, 7,or 6, respectively.
 7. An apparatus of a User Equipment (UE) fortransmitting Device-to-Device (D2D) data in a wireless communicationsystem, the apparatus comprising: a transmission module; and aprocessor, wherein the processor is configured to determine a bitmap tobe applied to a subframe pool for data transmission from a subframeindicator bitmap, determine a set of suframes to transmit the D2D databy using the bitmap to the subframe pool for data transmission, andtransmit the D2D data in a subframe included in the determined subframeset, wherein a set of values available as k being the number of 1s inthe subframe indicator bitmap are determined according to aUplink/Downlink (UL/DL) configuration set to which a UL/DL configurationconfigured for the UE belongs, wherein the UL/DL configuration setscomprise UL/DL configuration 1, 2, 4 and 5, UL/DL configuration 0 andUL/DL configurations 3 and 6, and wherein a value of 1 in the subframeindicator bitmap indicates the subframe used to transmit the D2D data.8. The apparatus according to claim 7, wherein if the UL/DLconfiguration configured for the UE is one of UL/DL configurations 1, 2,4 and 5, the set of values available as k is {1, 2, 4, 8}.
 9. Theapparatus according to claim 7, wherein if the UL/DL configurationconfigured for the UE is UL/DL configuration 0, the set of valuesavailable as k is {1, 2, 3, 4, 5, 6, 7}.
 10. The apparatus according toclaim 7, wherein if the UL/DL configuration configured for the UE is oneof UL/DL configurations 3 and 6, the set of values available as k is {1,2, 3, 4, 5, 6}.
 11. The apparatus according to claim 7, wherein the D2Ddata transmission is for transmission mode
 1. 12. The apparatusaccording to claim 7, wherein if the set of values available as k is {1,2, 4, 8}, {1, 2, 3, 4, 5, 6, 7}, or {1, 2, 3, 4, 5, 6}, the size of thesubframe indicator bitmap is 8, 7, or 6, respectively.